Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1999-02-22
2002-05-14
Evans, F. L. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S216000, C250S306000
Reexamination Certificate
active
06388239
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a scanning near-field optical microscope for observing microscopic features on and optical characteristics of the surface of a sample.
In general, conventional near-field optical, microscopes controlled by an atomic force have employed a probe which is obtained by sharpening an end of an optical propagation element such as an optical fiber, coating regions other than the end with a metal film and forming a microscopic aperture at the. end portion. While an optical fiber is primarily used as the optical propagation element, an optical fiber can not be used for observation at wavelengths in the ultraviolet region or infrared region which is important in the evaluation of physical properties because it allows propagation of beams having wavelengths generally about 350 to 1600 nm when used as a base material.
Under such circumstances, a probe has been proposed which has a hole that penetrates from an end of a probe made of silicon or silicon nitride for an atomic force microscope through a surface opposite thereto. In this case, since there is no solid substance that absorbs light in the hole connected to the aperture and the opposite surface, it is regarded usable for observation at wavelengths in the ultraviolet regions and infrared region.
Processes for manufacturing this type of probe for an atomic force microscope formed with a hole include a method wherein the hole is formed by etching and a method wherein the hole is formed by focused ion beams. According to the process utilizing etching, the hole is formed when etching proceeds to penetrate through, and etching must be stopped at a certain point in time. It is very difficult to perform etching while monitoring the formation of such a microscopic aperture and, consequently, it is quite difficult to control the size of the aperture formed. On the other hand, the method wherein the hole is formed using focused ion beams has a problem in that it results in low productivity and high manufacturing cost and has another problem in that a positional shift attributable to a drift of the focused ion beam apparatus results in the formation of a hole in a location other than an end of a probe.
In this regard, in order to spread near-field observation techniques in the ultraviolet region and infrared region, it is indispensable to provide a probe for a near-field optical microscope having good controllability on the formation of a microscopic aperture. One method for achieving this is a method reported by Lewis et al. and Shalone et al. utilizing a microscopic aperture at an end of a tube which has been thermally extended and cut away (U.S. Pat. No. 4,917,462 (1990); Rev. Sci. Instrum. 63 (1992) 4061). In this case, STM control or shear force control is employed to control the distance between a probe-and a sample. STM control has a problem in that a sample must be conductive. In the case of shear force control, although it can be used on a sample which is not conductive by oscillating the probe in the horizontal direction relative to the sample, it does not allow simultaneous observation of information relating to the physical properties of the surface of a sample, which is possible with AFM control. Here, the information, relating to physical properties includes friction, visco-elasticity, surface potential and the like, which can be detected by controlling a probe with a force in the vertical direction relative to a sample. Further, the shear force control method has a problem in that it occupies a greater space on the upper surface of a sample than in the AFM control method. The report of Shalone et al. discloses a tube probe which is bent to be usable as an AFM probe. In this case, however, since light can not be preferably propagated at the bent portion of the tube, it is difficult to provide light in an amount sufficient for measurement from a hole at the end thereof.
SUMMARY OF THE INVENTION
In order to solve the above-described problems, the inventors have conceived of a probe for a near-field optical microscope which is a thermally extended and cut away tube having a tapered portion and a microscopic aperture which part is configured as a thermally bent end portion in the form of a hook and has a structure wherein a part of the tube opposite to the microscopic aperture is removed to form an aperture at the removed portion and wherein there is no obstacle in the space between said aperture at the end.
The use of a glass tube as the above-described tube makes it possible to form a microscopic aperture and to manufacture a probe easily. In this case,.when light having a wavelength transmitted by glass is used, it is possible to prevent leakage of light because at least the outside of the tapered portion is coated with a material such as a metal which blocks an electromagnetic wave.
Further, when an optical lever method is used for controlling the distance between a sample and the probe based on atomic force control, more stable detection can be achieved by forming a mirrored surface on the surface of the tube opposite the aperture.
Furthermore, observation in the ultraviolet region and infrared region can be carried out by configuring a scanning near-field optical microscope with at least a light source, a collecting optical system, means for causing relative movement between a probe and a sample, an optical detector, and the above-described probe for a near-field optical microscope. This apparatus may have a configuration wherein collected light is introduced to said hole from the side of said probe opposite to the aperture and a configuration wherein detection light from the side of said probe opposite to the aperture is collected by an optical system.
REFERENCES:
patent: 622652 (1994-11-01), None
patent: 10-26628 (1998-01-01), None
patent: WO9503561 (1995-02-01), None
Patent Abstracts of Japan, vol. 095, No. 009 Oct. 31, 1995.
Patent Abstracts of Japan, vol. 097, No. 006 Jun. 30, 1997.
Patent Abstracts of Japan, vol. 095, No. 010 Nov. 30, 1995.
Adams & Wilks
Evans F. L.
Seiko Instruments Inc.
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